package com.pc;


import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 线程之间的通信问题：生产者和消费者问题    等待唤醒，通知唤醒
 * 线程交替执行：A,B操作同一个变量  num = 0
 * A:num+1
 * B:num-1
 * */
public class B {
    public static void main(String[] args) {
        Data2 data = new Data2();

        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.increment();
            }
        }, "A").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.decrement();
            }
        }, "B").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.increment();
            }
        }, "C").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.decrement();
            }
        }, "D").start();
    }
}


// JUC版的生产者和消费者
// 等待、业务、通知
// 资源类
class Data2 {
    private int num = 0;

    Lock lock = new ReentrantLock();
    // Condition:替代同步监视器
    Condition condition = lock.newCondition();
    //+1
    public void increment() {

        lock.lock();
        try {
            // 业务代码
            // 防止虚假唤醒：if => while
            while (num != 0) {
                // 等待
                condition.await();
            }
            num++;
            System.out.println(Thread.currentThread().getName() + "=>" + num);
            // 通知其他线程，我+1完了
            condition.signalAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }

    }

    //-1
    public void decrement() {
        lock.lock();
        try {
            while (num == 0) {
                // 等待
                condition.await();
            }
            num--;
            System.out.println(Thread.currentThread().getName() + "=>" + num);
            // 通知其他线程，我-1完了
            condition.signalAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}
